Osisko Intersects 1026 g/t Au Over 2.7 Metres at Lynx

Windfall Infill Drilling Continues to Confirm High-Grade

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TORONTO, Oct. 23, 2018 (GLOBE NEWSWIRE) -- Osisko Mining Inc. (OSK:TSX. "Osisko" or the "Corporation") is pleased to provide new infill drilling results from the ongoing drill definition and expansion program at its 100% owned Windfall Lake gold project located in the Abitibi greenstone belt, Urban Township, Eeyou Istchee James Bay, Québec. The 800,000 metre drill program commenced in late 2015. The program is currently focussed on infill drilling within the main Windfall gold deposit and the adjacent Lynx deposit (located immediately NE of Windfall), exploration and expansion drilling on the main mineralized zones, and deep exploration in the central areas of the intrusive system. Significant new analytical results from 37 intercepts in 17 drill holes and 6 wedges focused on infill drilling are presented below.

Highlights from the new results include: 1026 g/t Au over 2.7 metres in OSK-W-18-1725; 48.7 g/t Au over 3.3 metres in OSK-W-18-1560-W2; 59.3 g/t Au over 2.0 metres in OSK-W-18-1503-W1; 39.3 g/t Au over 2.3 metres in OSK-W-18-1665; 33.3 g/t Au over 2.7 metres in OSK-W-18-1711-W2 and 9.01 g/t Au over 9.2 metres in OSK-W-18-1402-W3. Maps showing hole locations and full analytical results are available at www.osiskomining.com.

Hole No.

From(m)

To(m)

Interval(m)

Au (g/t)uncut

Au (g/t)cut to100 g/t

Type

MineralizedZone

OSK-W-18-1402-W3

920.1

929.3

9.2

9.01

infill

Underdog

OSK-W-18-1475

258.8

261.0

2.2

8.09

infill

Lynx

including

258.8

259.1

0.3

36.1

OSK-W-18-1503-W1

406.8

409.1

2.3

5.09

infill

Lynx

including

407.5

408.3

0.8

11.3

420.0

422.0

2.0

59.3

36.4

infill

Lynx

including

420.7

421.4

0.7

166

100

430.5

432.5

2.0

29.7

15.5

infill

Lynx

including

431.2

431.5

0.3

195

100

OSK-W-18-1545

383.0

385.9

2.9

11.2

infill

Zone 27

OSK-W-18-1557

230.0

232.0

2.0

3.72

infill

Lynx

including

230.0

230.6

0.6

10.3

OSK-W-18-1560-W1

464.7

467.0

2.3

5.35

infill

Lynx

534.7

537.0

2.3

9.89

infill

Lynx

including

535.4

535.9

0.5

36.7

538.7

542.6

3.9

6.88

infill

Lynx

including

538.7

539.0

0.3

24.1

and

541.6

542.6

1.0

18.9

OSK-W-18-1560-W2

473.5

475.8

2.3

5.28

infill

Lynx

including

474.8

475.3

0.5

14.9

542.3

545.6

3.3

48.7

34.5

infill

Lynx

OSK-W-18-1587

198.1

200.1

2.0

10.0

infill

Lynx

OSK-W-18-1665

363.7

366.0

2.3

39.3

infill

Zone 27

including

365.0

366.0

1.0

72.2

OSK-W-18-1678

387.0

389.1

2.1

5.88

infill

Zone 27

including

388.8

389.1

0.3

40.0

OSK-W-18-1691

39.3

41.5

2.2

4.25

infill

Caribou

including

39.7

40.5

0.8

11.4

OSK-W-18-1707

153.1

155.4

2.3

3.95

infill

Caribou

199.0

201.0

2.0

6.23

infill

Caribou

380.0

382.4

2.4

27.4

infill

Zone 27

including

380.0

381.0

1.0

50.4

387.0

391.0

4.0

6.81

infill

Zone 27

OSK-W-18-1710

112.3

114.6

2.3

14.2

infill

Bobcat

OSK-W-18-1711

605.4

608.0

2.6

5.08

infill

Lynx

OSK-W-18-1711-W1

547.0

549.0

2.0

4.55

infill

Lynx

560.6

563.4

2.8

12.5

11.5

infill

Lynx

including

560.6

560.9

0.3

109

100

568.4

570.4

2.0

6.36

infill

Lynx

OSK-W-18-1711-W2

631.3

634.0

2.7

33.3

26.6

infill

Lynx

including

632.2

632.9

0.7

126

100

OSK-W-18-1712

210.0

212.2

2.2

5.14

infill

Lynx

including

210.4

211.2

0.8

13.0

OSK-W-18-1713

533.8

535.9

2.1

6.48

infill

Zone 27

OSK-W-18-1714

290.0

292.4

2.4

3.59

infill

Lynx

OSK-W-18-1723

488.4

490.6

2.2

22.7

infill

Lynx

498.6

501.2

2.6

4.06

infill

Lynx

including

500.8

501.2

0.4

25.3

OSK-W-18-1725

283.3

286.0

2.7

1026

64.8

infill

Lynx

including

283.3

284.0

0.7

502

100

and

284.4

285.3

0.9

2670

100

293.0

297.0

4.0

13.9

infill

Lynx

including

293.6

294.4

0.8

42.2

OSK-W-18-1727

169.0

171.0

2.0

6.51

infill

Lynx

including

169.0

169.8

0.8

15.6

OSK-W-18-1729

263.0

268.0

5.0

3.16

infill

Zone 27

272.5

274.8

2.3

7.00

infill

Zone 27

including

272.5

273.3

0.8

13.7

282.8

285.9

3.1

3.62

infill

Zone 27

including

282.8

283.2

0.4

20.0

Note: True widths are estimated at 65 – 80% of the reported core length interval. See "Quality Control and Reporting Protocols" below.

OSK-W-18-1503-W1 intersected three intervals in Lynx: 5.09 g/t Au over 2.3 metres, 59.3 g/t Au over 2.0 metres and 29.7 g/t Au over 2.0 metres. The first interval contains 5% disseminated/cluster pyrite, and up 3% pyrite/pyrite-tourmaline stringers within a weak fuchsite and sericite altered gabbro. The second interval contains local visible gold in pyrite stringers and trace chalcopyrite within a moderate sericite altered rhyolite. The third interval has local visible gold and electrum within centimetre scale smoky quartz veins, hosted in a moderate sericite altered rhyolite.

OSK-W-18-1557 intersected 3.72 g/t Au over 2.0metres in Lynx. Mineralization consists of up to 40% pyrite as stringers and patches with ptygmatic tourmaline veinlets and breccia quartz-carbonate veins hosted at the contact between a fuchsite, sericite and chlorite altered gabbro and a moderate sericite altered fragmental felsic intrusion.

OSK-W-18-1560-W1 intersected three intervals in Lynx: 5.35 g/t Au over 2.3 metres, 9.89 g/t Au over 2.3 metres and 6.88 g/t Au over 3.9 metres. The first interval contains up to 7% pyrite stringers, 5% pyrite in smoky quartz veins, 2% pyrite in dismembered tourmaline ptygmatic veins, 10% disseminated and clustered pyrite in a sericitized and silicified rhyolite. The second interval contains 7% disseminated pyrite and 5% pyrite within quartz-carbonate veins hosted in a sericite, silica and fuchsite altered gabbro. The third interval contains up to 7% disseminated pyrite, 5% pyrite in quartz-carbonate veins hosted in a bleached, sericitized and silicified gabbro.

OSK-W-18-1560-W2 intersected two intervals in Lynx 5.28 g/t Au over 2.3metres and 48.7 g/t Au over 3.3 metres. The first interval contains up to 10% pyrite stringers, 10% pyrite with pervasive silica flooding, 10% disseminated pyrite and 3% disseminated chalcopyrite. The mineralization is hosted in an alternation between bleached, sericitized and silicified gabbro and sericitized rhyolite. The second interval contains up to 20% disseminated pyrite, 20% pyrite stringers, 5% pyrite within quartz-tourmaline veins and 1% hosted in a silica, fuchsite and sericite altered gabbro.

OSK-W-18-1587 intersected 10.0 g/t Au over 2.0 metres in Lynx. Mineralization consists of 4% disseminated pyrite and ptygmatic quartz-tourmaline veins within a strong sericite and silica altered contact between a gabbro and a rhyolite.

OSK-W-18-1729 intersected three intervals in Zone 27: 3.16 g/t Au over 5.0 metre, 7.00 g/t Au over 2.3 metres and 3.62 g/t Au over 3.1 metres. The first interval contains 10% pyrite stringers with local tourmaline ptygmatic veins hosted at the contact between a moderate sericite and weak silicified altered felsic porphyritic dike and a moderate sericite altered andesite. The second interval contains 7% pyrite stringers and up to 20% pyrite in pervasive silica flooding within a silicified and sericitized porphyritic felsic intrusion. The third interval contains up to 5% pyrite stringers, 3% pyrite with ptygmatic tourmaline veins and 3% disseminated pyrite within a moderate sericite and weak silica altered felsic porphyritic intrusion.

Qualified Person The scientific and technical content of this news release has been reviewed, prepared and approved by Mr. Louis Grenier, M.Sc.A., P.Geo. (OGQ 800), Project Manager of Osisko's Windfall Lake gold project, who is a "qualified person" as defined by National Instrument 43-101 – Standards of Disclosure for Mineral Projects ("NI 43-101").

Quality Control and Reporting ProtocolsTrue width determination is currently unknown but is estimated at 65-80% of the reported core length interval for the zone. Assays are uncut except where indicated. Intercepts occur within geological confines of major zones but have not been correlated to individual vein domains at this time. Reported intervals include minimum weighted averages of 3.0 g/t Au diluted over core lengths of at least 2.0 metres. All NQ core assays reported were obtained by either 1-kilogram screen fire assay or standard 50-gram fire-assaying-AA finish or gravimetric finish at (i) ALS Laboratories in Val d'Or, Québec, Thunder Bay, Ontario, Sudbury, Ontario or Vancouver, British Colombia, or (ii) Bureau Veritas in Timmins, Ontario. The 1-kilogram screen assay method is selected by the geologist when samples contain coarse gold or present a higher percentage of pyrite than surrounding intervals. Selected samples are also analyzed for multi-elements, including silver, using an Aqua Regia-ICP-AES method at ALS Laboratories. Drill program design, Quality Assurance/Quality Control ("QA/QC") and interpretation of results is performed by qualified persons employing a QA/QC program consistent with NI 43-101 and industry best practices. Standards and blanks are included with every 20 samples for QA/QC purposes by the Corporation as well as the lab. Approximately 5% of sample pulps are sent to secondary laboratories for check assay.

About the Windfall Lake Gold DepositThe Windfall Lake gold deposit is located between Val-d'Or and Chibougamau in the Abitibi region of Québec, Canada. The mineral resource defined by Osisko, as disclosed in the Windfall Lake Technical Report (as defined below), comprises 2,382,000 tonnes at 7.85 g/t Au (601,000 ounces) in the indicated mineral resource category and 10,605,000 tonnes at 6.70 g/t Au (2,284,000 ounces) in the inferred mineral resource category. For details regarding the key assumptions, parameters and methods used to estimate the mineral resources presented in respect of the Windfall Lake gold project, please see the technical report entitled "Technical Report and Mineral Resource Estimate for the Windfall Lake Project, Windfall Lake and Urban-Barry Properties" and dated June 12, 2018 (effective date of May 14, 2018), which has been prepared by InnovExplo Inc. from Val-d'Or, Québec (the "Windfall Lake Technical Report"). The Windfall Lake Technical Report is available on Osisko's website at www.osiskomining.com and on SEDAR under Osisko's issuer profile at www.sedar.com). The Windfall Lake gold deposit is currently one of the highest grade resource-stage gold projects in Canada. Mineralization occurs in four principal zones: Lynx, Zone 27, Caribou and Underdog. All zones comprise sub-vertical lenses following intrusive porphyry contacts plunging to the northeast. The deposit is well defined from surface to a depth of 900 metres and remains open along strike and at depth. Mineralization has been identified 30 metres from surface in some areas and as deep as 2000 metres in others, with significant potential to extend mineralization down-plunge and at depth.

About Osisko Mining Inc.Osisko is a mineral exploration company focused on the acquisition, exploration, and development of precious metal resource properties in Canada. Osisko holds a 100% in the high-grade Windfall Lake gold deposit located between Val-d'Or and Chibougamau in Québec and holds a 100% undivided interest in a large area of claims in the surrounding Urban Barry area and nearby Quevillon area (over 3,300 square kilometres), a 100% interest in the Marban project located in the heart of Québec's prolific Abitibi gold mining district, and properties in the Larder Lake Mining Division in northeast Ontario, including the Jonpol and Garrcon deposits on the Garrison property, the Buffonta past producing mine and the Gold Pike mine property. The Corporation also holds interests and options in a number of additional properties in northern Québec and Ontario.

Cautionary Note Regarding Forward-Looking InformationThis news release contains "forward-looking information" within the meaning of the applicable Canadian securities legislation that is based on expectations, estimates, projections and interpretations as at the date of this news release. The information in this news release about the Windfall Lake gold deposit being one of the highest grade resource-stage gold projects in Canada; the Windfall Lake gold deposit being a world-class gold system; the significance of new results from the ongoing deep-hole drill/exploration program at the Windfall Lake gold project; the significance of assay results presented in this news release; potential depth extensions of the Lynx and Underdog mineralized zones; the potential, if any of the Deep Underdog and Deep Lynx zones; the type and extend of drilling on the Deep Underdog and Deep Lynx zones, including planned wedge holes; the success of Osisko's deep-hole drill/exploration program at the Windfall Lake gold project, if any; the down-plunge projection of the gold mineralized structures; the current 800,000 metre drill program; the type of drilling included in the drill program; potential mineralization; the potential to extend mineralization up and down-plunge and at depth at the Windfall Lake gold deposit; the ability to realize upon any mineralization in a manner that is economic; the ability to complete any proposed exploration activities and the results of such activities, including the continuity or extension of any mineralization; and any other information herein that is not a historical fact may be "forward-looking information". Any statement that involves discussions with respect to predictions, expectations, interpretations, beliefs, plans, projections, objectives, assumptions, future events or performance (often but not always using phrases such as "expects", or "does not expect", "is expected", "interpreted", "management's view", "anticipates" or "does not anticipate", "plans", "budget", "scheduled", "forecasts", "estimates", "believes" or "intends" or variations of such words and phrases or stating that certain actions, events or results "may" or "could", "would", "might" or "will" be taken to occur or be achieved) are not statements of historical fact and may be forward-looking information and are intended to identify forward-looking information. This forward-looking information is based on reasonable assumptions and estimates of management of the Corporation at the time such assumptions and estimates were made, and involves known and unknown risks, uncertainties and other factors which may cause the actual results, performance or achievements of Osisko to be materially different from any future results, performance or achievements expressed or implied by such forward-looking information. Such factors include, among others, risks relating to the ability of exploration activities (including drill results) to accurately predict mineralization; errors in management's geological modelling; the ability of Osisko to complete further exploration activities, including drilling; property interests in the Windfall Lake gold project; the ability of the Corporation to obtain required approvals and complete transactions on terms announced; the results of exploration activities; risks relating to mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions. Although the forward-looking information contained in this news release is based upon what management believes, or believed at the time, to be reasonable assumptions. Osisko cannot assure shareholders and prospective purchasers of securities of the Corporation that actual results will be consistent with such forward-looking information, as there may be other factors that cause results not to be as anticipated, estimated or intended, and neither Osisko nor any other person assumes responsibility for the accuracy and completeness of any such forward-looking information, Osisko does not undertake, and assumes no obligation, to update or revise any such forward-looking statements or forward-looking information contained herein to reflect new events or circumstances, except as may be required by law.

For further information please contact:John Burzynski President and Chief Executive OfficerTelephone: (416) 363-8653